registry_rebuild_cache throws notices

On enabling modules, these error messages are logged:

    * notice: Undefined index: files in includes/registry.inc on line 33.
    * warning: Invalid argument supplied for foreach() in includes/registry.inc on line 33.

This is the code:

function _drupal_rebuild_code_registry() {
  // Reset the resources cache.
  _registry_get_resource_name();
  // Get the list of files we are going to parse.
  $files = array();
  foreach (module_rebuild_cache() as $module) {
    if ($module->status) {
      $dir = dirname($module->filename);
      foreach ($module->info['files'] as $file) { // #33
        $files["./$dir/$file"] = array();
      }

Presumably, the module data generated by module_rebuild_cache will sometimes not contain a files element. I am not sure if this is a bug in the module concerned, or a bug in the registry.